1. Field of the Invention
Over the past decade, there have been numerous reports relating to the identification of tumor associated antigens, also referred to as tumor markers. Such tumor associated antigens may be intracellular or cell surface molecules, typically proteins, glycoproteins, glycolipids, and the like, which are associated with neoplastic cells but not with corresponding normal cells or are associated with normal cells in very small quantities. In some instances, the tumor associated antigens are released from the neoplastic cells into the blood or body fluids, and many attempts have been made to correlate the serum level of such antigens with the presence and/or status of the disease.
Unfortunately, such correlations have been very difficult to make. Ideally, a useful tumor marker would be present in all patients suffering from the tumor, but would be absent from the sera of all normal patients and patients suffering from other types of neoplasia. At present, no such tumor markers have been identified. Instead, it has been found frequently that markers which are identified with the neoplastic transformation of one type of cell will be present on cells of other normal tissues. Conversely, it is also found that markers associated with particular types of tumors in a number of individual patients will not be universally associated with that type of tumor on all patients. Thus, serum assays for virtually all known tumor markers are subject to false positives stemming from release of "tumor" markers from normal cells and false negatives resulting from the lack of universal tumor markers.
For these reasons, it would be desirable to provide improved tumor marker assays capable of furnishing a superior correlation between the presence of the tumor marker and the disease state of the patient. It would be particularly desirable to provide such assays which may be employed with both known and presently undiscovered tumor markers.
2. Description of the Prior Art
Gupta et al. (1983) Clin. Exp. Immunol. 53:589-599 describes the detection of tumor associated antigen in eluates from Staphylococcus aureus columns used for the immunoadsorption of plasma from a melanoma patient. Theofilopoulous et al. (1978) J. Clin. Invest. 59:1570-1581 describe an assay for immune complexes employing Raji cells for binding of the immune complexes.